pixell

pixell is a library for loading, manipulating and analyzing maps stored in rectangular pixelization. It is mainly targeted for use with maps of the sky (e.g. CMB intensity and polarization maps, stacks of 21 cm intensity maps, binned galaxy positions or shear) in cylindrical projection, but its core functionality is more general. It extends numpy's ndarray to an ndmap class that associates a World Coordinate System (WCS) with a numpy array. It includes tools for Fourier transforms (through numpy or pyfft) and spherical harmonic transforms (through ducc0) of such maps and tools for visualization (through the Python Image Library).

• Free software: BSD license
• Documentation: https://pixell.readthedocs.io.
• Tutorials

Dependencies

• Python>=3.7
• gcc/gfortran or Intel compilers (clang might not work out of the box), if compiling from source
• ducc0, healpy, Cython, astropy, numpy, scipy, matplotlib, pyyaml, h5py, Pillow (Python Image Library)

Installing

Make sure your pip tool is up-to-date. To install pixell, run:

$ pip install pixell --user
$ test-pixell

This will install a pre-compiled binary suitable for your system (only Linux and Mac OS X with Python>=3.7 are supported). Note that you need ~/.local/bin to be in your PATH for the latter test-pixell to work.

If you require more control over your installation, e.g. using Intel compilers, please see the section below on compiling from source. The test-pixell command will run a suite of unit tests.

Compiling from source (advanced / development workflow)

For compilation instructions specific to NERSC/cori, see NERSC.

For all other, below are general instructions.

First, download the source distribution or git clone this repository. You can work from master or checkout one of the released version tags (see the Releases section on Github). Then change into the cloned/source directory.

Run setup.py

If not using Intel compilers (see below), build the package using

$ python setup.py build_ext -i

You may now test the installation:

$ py.test pixell/tests/

If the tests pass, either add the cloned directory to your $PYTHONPATH, if you want the ability for changes made to Python source files to immediately reflect in your installation, e.g., in your .bashrc file,

export PYTHONPATH=$PYTHONPATH:/path/to/cloned/pixell/directory

or alternatively, install the package

$ python setup.py install --user

which requires you to reinstall every time changes are made to any files in your repository directory.

Intel compilers

Intel compilers require you to modify the build step above as follows

$ python setup.py build_ext -i --fcompiler=intelem --compiler=intelem

On some systems, further specification might be required (make sure to get a fresh copy of the repository before trying out a new install method), e.g.:

$ LDSHARED="icc -shared" LD=icc LINKCC=icc CC=icc python setup.py build_ext -i --fcompiler=intelem --compiler=intelem

Contributions

If you have write access to this repository, please:

1. create a new branch
2. push your changes to that branch
3. merge or rebase to get in sync with master
4. submit a pull request on github

If you do not have write access, create a fork of this repository and proceed as described above. For more details, see Contributing.